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Merge pull request #40732 from slavapestov/rqm-layout-requirement-rel…
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RequirementMachine: Minimization understands 'relations' among layout requirements
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@slavapestov
slavapestov committed Jan 5, 2022
2 parents cb0c527 + 66cf913 commit cc12c4e
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Showing 9 changed files with 321 additions and 125 deletions.
13 changes: 8 additions & 5 deletions lib/AST/RequirementMachine/HomotopyReduction.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -88,15 +88,16 @@ RewriteLoop::findRulesAppearingOnceInEmptyContext(
switch (step.Kind) {
case RewriteStep::ApplyRewriteRule: {
if (!step.isInContext() && !evaluator.isInContext())
rulesInEmptyContext.insert(step.RuleID);
rulesInEmptyContext.insert(step.getRuleID());

++ruleMultiplicity[step.RuleID];
++ruleMultiplicity[step.getRuleID()];
break;
}

case RewriteStep::AdjustConcreteType:
case RewriteStep::Shift:
case RewriteStep::Decompose:
case RewriteStep::Relation:
case RewriteStep::ConcreteConformance:
case RewriteStep::SuperclassConformance:
case RewriteStep::ConcreteTypeWitness:
Expand Down Expand Up @@ -207,7 +208,7 @@ RewritePath RewritePath::splitCycleAtRule(unsigned ruleID) const {
for (auto step : Steps) {
switch (step.Kind) {
case RewriteStep::ApplyRewriteRule: {
if (step.RuleID != ruleID)
if (step.getRuleID() != ruleID)
break;

assert(!sawRule && "Rule appears more than once?");
Expand All @@ -220,6 +221,7 @@ RewritePath RewritePath::splitCycleAtRule(unsigned ruleID) const {
case RewriteStep::AdjustConcreteType:
case RewriteStep::Shift:
case RewriteStep::Decompose:
case RewriteStep::Relation:
case RewriteStep::ConcreteConformance:
case RewriteStep::SuperclassConformance:
case RewriteStep::ConcreteTypeWitness:
Expand Down Expand Up @@ -262,7 +264,7 @@ bool RewritePath::replaceRuleWithPath(unsigned ruleID,

for (const auto &step : Steps) {
if (step.Kind == RewriteStep::ApplyRewriteRule &&
step.RuleID == ruleID) {
step.getRuleID() == ruleID) {
foundAny = true;
break;
}
Expand All @@ -282,7 +284,7 @@ bool RewritePath::replaceRuleWithPath(unsigned ruleID,
for (const auto &step : Steps) {
switch (step.Kind) {
case RewriteStep::ApplyRewriteRule: {
if (step.RuleID != ruleID) {
if (step.getRuleID() != ruleID) {
newSteps.push_back(step);
break;
}
Expand Down Expand Up @@ -321,6 +323,7 @@ bool RewritePath::replaceRuleWithPath(unsigned ruleID,
case RewriteStep::AdjustConcreteType:
case RewriteStep::Shift:
case RewriteStep::Decompose:
case RewriteStep::Relation:
case RewriteStep::ConcreteConformance:
case RewriteStep::SuperclassConformance:
case RewriteStep::ConcreteTypeWitness:
Expand Down
12 changes: 7 additions & 5 deletions lib/AST/RequirementMachine/MinimalConformances.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -113,7 +113,7 @@ void RewriteLoop::findProtocolConformanceRules(
if (!evaluator.isInContext()) {
switch (step.Kind) {
case RewriteStep::ApplyRewriteRule: {
const auto &rule = system.getRule(step.RuleID);
const auto &rule = system.getRule(step.getRuleID());

if (rule.isIdentityConformanceRule())
break;
Expand All @@ -127,7 +127,7 @@ void RewriteLoop::findProtocolConformanceRules(
// the prefix term is 'X'.
const auto &term = evaluator.getCurrentTerm();
MutableTerm prefix(term.begin(), term.begin() + step.StartOffset);
result[proto].RulesInContext.emplace_back(prefix, step.RuleID);
result[proto].RulesInContext.emplace_back(prefix, step.getRuleID());
}
}

Expand All @@ -137,6 +137,7 @@ void RewriteLoop::findProtocolConformanceRules(
case RewriteStep::AdjustConcreteType:
case RewriteStep::Shift:
case RewriteStep::Decompose:
case RewriteStep::Relation:
case RewriteStep::ConcreteConformance:
case RewriteStep::SuperclassConformance:
case RewriteStep::ConcreteTypeWitness:
Expand Down Expand Up @@ -262,7 +263,7 @@ MinimalConformances::decomposeTermIntoConformanceRuleLeftHandSides(
const auto &step = *steps.begin();

#ifndef NDEBUG
const auto &rule = System.getRule(step.RuleID);
const auto &rule = System.getRule(step.getRuleID());
assert(rule.isAnyConformanceRule());
assert(!rule.isIdentityConformanceRule());
#endif
Expand All @@ -277,9 +278,10 @@ MinimalConformances::decomposeTermIntoConformanceRuleLeftHandSides(
// Build the term U.
MutableTerm prefix(term.begin(), term.begin() + step.StartOffset);

decomposeTermIntoConformanceRuleLeftHandSides(prefix, step.RuleID, result);
decomposeTermIntoConformanceRuleLeftHandSides(
prefix, step.getRuleID(), result);
} else {
result.push_back(step.RuleID);
result.push_back(step.getRuleID());
}
}

Expand Down
2 changes: 1 addition & 1 deletion lib/AST/RequirementMachine/PropertyMap.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -319,7 +319,7 @@ Optional<unsigned> PropertyMap::addProperty(
assert(*System.getRule(ruleID).isPropertyRule() == property);
auto *props = getOrCreateProperties(key);
bool debug = Debug.contains(DebugFlags::ConcreteUnification);
return props->addProperty(property, ruleID, Context,
return props->addProperty(property, ruleID, System,
inducedRules, debug);
}

Expand Down
2 changes: 1 addition & 1 deletion lib/AST/RequirementMachine/PropertyMap.h
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Original file line number Diff line number Diff line change
Expand Up @@ -103,7 +103,7 @@ class PropertyBag {

Optional<unsigned> addProperty(Symbol property,
unsigned ruleID,
RewriteContext &ctx,
RewriteSystem &system,
SmallVectorImpl<InducedRule> &inducedRules,
bool debug);
void copyPropertiesFrom(const PropertyBag *next,
Expand Down
115 changes: 108 additions & 7 deletions lib/AST/RequirementMachine/PropertyUnification.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,82 @@
using namespace swift;
using namespace rewriting;

unsigned RewriteSystem::recordRelation(Symbol lhs, Symbol rhs) {
auto key = std::make_pair(lhs, rhs);
auto found = RelationMap.find(key);
if (found != RelationMap.end())
return found->second;

unsigned index = Relations.size();
Relations.push_back(key);
auto inserted = RelationMap.insert(std::make_pair(key, index));
assert(inserted.second);
(void) inserted;

return index;
}

RewriteSystem::Relation
RewriteSystem::getRelation(unsigned index) const {
return Relations[index];
}

/// Given two property rules (T.[p1] => T) and (T.[p2] => T) where [p1] < [p2],
/// record a rewrite loop that makes the second rule redundant from the first.
static void recordRelation(unsigned lhsRuleID, unsigned rhsRuleID,
RewriteSystem &system,
SmallVectorImpl<InducedRule> &inducedRules,
bool debug) {
const auto &lhsRule = system.getRule(lhsRuleID);
const auto &rhsRule = system.getRule(rhsRuleID);

auto lhsProperty = lhsRule.getLHS().back();
auto rhsProperty = rhsRule.getLHS().back();

assert(lhsProperty.isProperty());
assert(rhsProperty.isProperty());
assert(lhsProperty.getKind() == rhsProperty.getKind());

if (debug) {
llvm::dbgs() << "%% Recording relation: ";
llvm::dbgs() << lhsRule.getLHS() << " < " << rhsProperty << "\n";
}

unsigned relationID = system.recordRelation(lhsProperty, rhsProperty);

/// Build the following rewrite path:
///
/// (T => T.[p1]).[p2] ⊗ T.Relation([p1].[p2] => [p1]) ⊗ (T.[p1] => T).
///
RewritePath path;

/// Starting from T.[p2], the LHS rule in reverse to get T.[p1].[p2].
path.add(RewriteStep::forRewriteRule(/*startOffset=*/0,
/*endOffset=*/1,
/*ruleID=*/lhsRuleID,
/*inverse=*/true));

/// T.Relation([p1].[p2] => [p1]).
path.add(RewriteStep::forRelation(relationID, /*inverse=*/false));

/// (T.[p1] => T).
path.add(RewriteStep::forRewriteRule(/*startOffset=*/0,
/*endOffset=*/0,
/*ruleID=*/lhsRuleID,
/*inverse=*/false));

/// Add the rule (T.[p2] => T) with the above rewrite path.
///
/// Since a rule (T.[p2] => T) *already exists*, both sides of the new
/// rule will simplify down to T, and the rewrite path will become a loop.
///
/// This loop encodes the fact that (T.[p1] => T) makes (T.[p2] => T)
/// redundant.
inducedRules.emplace_back(MutableTerm(rhsRule.getLHS()),
MutableTerm(rhsRule.getRHS()),
path);
}

/// This method takes a concrete type that was derived from a concrete type
/// produced by RewriteSystemBuilder::getConcreteSubstitutionSchema(),
/// either by extracting a structural sub-component or performing a (Swift AST)
Expand Down Expand Up @@ -310,7 +386,7 @@ static std::pair<Symbol, bool> unifySuperclasses(
/// Returns the old conflicting rule ID if there was a conflict,
/// otherwise returns None.
Optional<unsigned> PropertyBag::addProperty(
Symbol property, unsigned ruleID, RewriteContext &ctx,
Symbol property, unsigned ruleID, RewriteSystem &system,
SmallVectorImpl<InducedRule> &inducedRules,
bool debug) {

Expand All @@ -320,18 +396,41 @@ Optional<unsigned> PropertyBag::addProperty(
ConformsToRules.push_back(ruleID);
return None;

case Symbol::Kind::Layout:
case Symbol::Kind::Layout: {
auto newLayout = property.getLayoutConstraint();

if (!Layout) {
Layout = property.getLayoutConstraint();
// If we haven't seen a layout requirement before, just record it.
Layout = newLayout;
LayoutRule = ruleID;
} else {
// Otherwise, compute the intersection.
assert(LayoutRule.hasValue());
Layout = Layout.merge(property.getLayoutConstraint());
if (!Layout->isKnownLayout())
auto mergedLayout = Layout.merge(property.getLayoutConstraint());

// If the intersection is invalid, we have a conflict.
if (!mergedLayout->isKnownLayout())
return LayoutRule;

// If the intersection is equal to the existing layout requirement,
// the new layout requirement is redundant.
if (mergedLayout == Layout) {
recordRelation(*LayoutRule, ruleID, system, inducedRules, debug);

// If the intersection is equal to the new layout requirement, the
// existing layout requirement is redundant.
} else if (mergedLayout == newLayout) {
recordRelation(ruleID, *LayoutRule, system, inducedRules, debug);
LayoutRule = ruleID;
} else {
llvm::errs() << "Arbitrary intersection of layout requirements is "
<< "supported yet\n";
abort();
}
}

return None;
}

case Symbol::Kind::Superclass: {
// FIXME: Also handle superclass vs concrete
Expand All @@ -342,7 +441,8 @@ Optional<unsigned> PropertyBag::addProperty(
} else {
assert(SuperclassRule.hasValue());
auto pair = unifySuperclasses(*Superclass, property,
ctx, inducedRules, debug);
system.getRewriteContext(),
inducedRules, debug);
Superclass = pair.first;
bool conflict = pair.second;
if (conflict)
Expand All @@ -359,7 +459,8 @@ Optional<unsigned> PropertyBag::addProperty(
} else {
assert(ConcreteTypeRule.hasValue());
bool conflict = unifyConcreteTypes(*ConcreteType, property,
ctx, inducedRules, debug);
system.getRewriteContext(),
inducedRules, debug);
if (conflict)
return ConcreteTypeRule;
}
Expand Down

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